1. Field of the Invention
The invention is related to providing a pretensioner of a safety belt retractor, and particularly, to a pretensioner integrated with a force transmitting apparatus of a seat belt retractor for reverse-rotating a reel of the retractor on which the safety belt is wound, forcedly, and transmitting the force to tighten the safety belt on an occupant""s body upon the occurrence of accident.
2. Discussion of the Background
Until now, much effort has been given on the basic performance of a car such as a comfortable feeling during driving, the speed as well as on a safety apparatuses for protecting passengers. Especially, it is well-known that a safety belt retractor has been significantly developed in its safety performance in respect to passengers, and a pretensioner also has been matched up with the safety belt retractor to enhance the inherent performance of the safety belt retractor. The pretensioner reversely rotates a retractor reel to pull a predetermined length of the safety belt by the power of a power generator using a Pyrotechnic for generating gas or other powers upon the sudden deceleration of the car, for example a crash or an accident. But, it is not certain that the pretensioner already developed would be able to comply with the inherent purpose of restraining the passenger in the seat. The reason is because the technical difficulties exist in adjusting the rewinding length of the safety belt according to the generating power due to the separation of the pretensioner from the generating apparatus.
A typical example of this technique is U.S. Pat. No. 3,043,093 which describes an actuator operated by a gas pressure. The actuator includes a piston which is movably disposed in a cylinder. The cylinder is closed at one end by a bracket and has a gas inlet port through which a gas under pressure may be delivered from any suitable source. A pulley is pivoted in the piston and journaled to cooperate with a cable. The cable has one of its ends from which it passes over a pulley to another pulley fixed to a shaft. On the same shaft as the pulley are a first pulley and a second pulley. The first pulley functions through a cable to operate a load device such as a belt, and the second pulley functions through a web to operate another load device such as means for positioning the shoulders of a pilot. Herein, it is known that the pulley of the shaft and the cylinder including a piston are mounted as the actuator having the same function as the pretensioner. But, the actuator has a possibility to distort the operation of the shaft pulley due to the reverse operation of the first and second pulley against each other, thereby not securing the moving distance of the piston, namely the rewinding length of the belt.
Another example adopting the patent to a vehicle is U.S. Pat. No. 4,423,846 which discloses a retightener for automatic safety belt roll-up devices with a power reservoir, which can be triggered in case of a crash and with an energy transducer which acts upon the belt shaft of the automatic winder after triggering the power reservoir, causing the automatic winder to perform a rotary retightening motion. For example, the retightener is provided with an automatic safety belt winder. A belt shaft is extended beyond a rewind spring cover by a shaft extension. The face of the shaft extension has sawtooth-shaped axial teeth which can be coupled to correspond to sawtooth-shaped and axial counter teeth of pulling means pulley. Serving the mounting of the pulling means pulley is a trunnion which is molded on a cup-shaped cover and permanently joined to the automatic winder housing or screwed by screws to the cover. The pulling means pulley is axially movable on the trunnion. Four cams are molded to the cover in the form of curved protruding in corresponding recesses with slanted, wedge-shaped strike surfaces in the pulling means pulley. A shear pin is fixed in the cover and projects into a hole in the pulling means pulley, fixing the latter in the inoperative, inactivated position. A cable or pulling means is connected to the pulling means pulley. Upon tension of the cable, the shear pin is sheared off, and at the same time the pulling means pulley is moved axial towards the axial teeth via cams, so that a coupling connection of the counter teeth and the axial teeth is established. This couples the belt shaft to the pulling means pulley, to the cable and to a preceding power reservoir drive. Consequently, the belt is tightened by turning the belt shaft again.
But, the retightener requires larger care in withdrawing a predetermined length of a belt because the cable length to be withdrawn is varied dependent upon the position of the pin. Also, because the retightener requires an auxiliary mechanism to be mounted for the operation of the pulling means pulley along with a power reservoir, the mounting of the safety belt retractor provided with the retightener is limited in respect of having to secure a space in the vehicle.
To overcome these disadvantages, a seat belt retractor with a pretensioner is disclosed in U.S. Pat. No. 5,489,072. As shown in FIG. 1, the retractor includes a spring casing 2 mounted on one side thereof and a spring 1 of a clock spring type retained in the spring casing 2, in which one end of the spring 1 is fixed to the fixing groove formed on the inner surface of the spring casing 2, and other end positioned in the center of the spring 1 is fixed to a fixing arbor 8 of the spring casing 2. The spring casing 2 is mounted on the side of a pretensioner housing 3. A reel 4 on which a safety belt is wound is rotatably mounted on an U-shaped bracket 6 by means of a shaft coupling member such as a bearing (not shown).
A pretensioner is mounted between the bracket 6 and the spring casing 2 and includes the housing 3 and a pyrotechnic force generator 21. The housing 3 is provided with a clutch drum 18, including three internal actuated indentations of an approximate triangle in the form of a pulley and three rollers 15. The housing 3 is provided with two frangible pins 12 integrally moulded on its interior and three integrally moulded frangible pegs 14 rotatably carrying each of roller 15.
Upon mounting of the pretensioner, each of the rollers 15 is seated on the rounded corner of the indentations 16 in the clutch drum 18 while being rotatably mounted on the pegs 14. The clutch drum 18 is mounted in the inner portion of the housing 3 with apertures 13 being coupled with the pins 12, respectively. Also, on the periphery of the clutch drum 18 there is formed a groove corresponding to a cable 19 with both side surfaces 17. A center shaft 10 of the reel 4 is passed through the indentation 16 of the clutch drum 18 and a hole of the housing 3 and then fixed to the fixing arbor 8. The cable 19 is turned over the groove of the clutch drum several times. One end of the cable 19 wound is fixed to the periphery of the clutch drum 18 and other end is connected to the pyrotechnic force generator 21. The pyrotechnic force generator 21 serves to pull the cable 19 connected to a piston (not shown) upward, when the vehicle is abruptly decelerated and an igniter (not shown) is detonated. At that time, the cable 19 rotates the clutch drum 18, and the frangible pins 12 are sheared. Then, the pegs 14 are sheared to enable the rollers 15 to be trapped in the locking position between the cam surfaces of the indentations 16 and the outer surface of the center shaft 10, thereby rotating the reel 4 by a predetermined number.
But, the pretensioner cannot have a predetermined withdrawal length of the cable, because the cable length is changeable according to the position of the cable fixing end on the periphery of the clutch drum, and the distance of play for coupling the rollers with the center shaft exists.
Furthermore, U.S. Patent ""846 or ""072 is subject to break the pins upon reverse-rotating of the clutch drum or the pulley using a power from a pyrotechnic force generator, but it is not certain that the clutch drum or the pulley may be not reverse-rotated on time. The patents requires a relative longer cable, because the pyrotechnic force generator has a relative longer length and a larger volume with a straight cylinder to turn the predetermined number of the drum or pulley. Due to this, the pretensioners have disadvantages in that the traveling length of the cable becomes longer, thereby deteriorating the response characteristics of the pretensioner. Especially, U.S. Patent ""072 has a disadvantage in that the center shaft of a reel may be distorted or broken in a structural respect because the exceeding friction force may be generated upon the coupling of the rollers with the inner surface of an indentation to cause the center shaft to be trapped therebetween.
On the other hand, U.S. Pat. No. 5,588,608 and Japanese Unexamined Patent Publication No. Hei8-26070 discloses a pretensioner that reduces the traveling or driving length of a cable according to the rotation of a clutch drum or pulley. These patents comprise a webbing take-up device equipped with a pretensioner. The pretensioner includes a clutch mechanism and a gas generating device, wherein the generating device includes a cylinder attached alongside the webbing take-up device. The cylinder includes a box shaped piston disposed inside and the piston includes a pulley axially supported therein, which a wire is wound thereon. A gas generating device is mounted on the bottom portion of the cylinder. A wire is fixed at one end on the bottom surface of the cylinder and passed through the pulley on the piston and other pulley in turns. The other end of the wire is wound around and fixed to a rotating drum cooperating with a retractor reel. Therefore, when a predetermined gas pressure is generated from the gas generating device, as the piston is moved upward and the piston pulley is rotated, the wire is pulled through the other pulley to rotate the rotating drum and the retractor reel as well.
Japanese Unexamined Patent No. Hei 8-26070 discloses an improved technical contents of Patent ""608, which is related to a wire holding structure of a pretensioner for shifting a piston, pulling a wire and drawing a wire out of a drum during the generating of gas. The direction of the wire between a first guide outside a cylinder and a second guide of a piston in the cylinder is tilted with respect to the piston shift direction. For it, the wire penetrates through the inside and outside a hole installed on a cylinder end wall to allow it the wire to establish the sealing of the cylinder. Also, the wire is wound around and penetrates through the cylinder which is then wound around the piston to increase its length.
Those patents can reduce the size of the gas generating device by extending the traveling length of the wire or cable, but the gas generating device is subject to mounting its cylinder separately from the wire drum or pulley. This means that a number of limitations exist in securing double mounting spaces. Particularly, because the pulley or the guide is positioned below the cable pulley or the wire drum thereby to form a gap between them, and the traveling distance of the wire is extended by the gap. Therefore, in order to minimize the traveling distance, the drum and the piston are preferably positioned to be on the same line. This means the exact adjustment of the traveling distance of the cable or wire is required. In order to resolve these problems of cited prior arts, the main object of the invention is to provide a pretensioner mounted on one side of a retractor and integrated with a gas generating apparatus for improving the performance of the force transmitting portion compared with a relative shorter traveling distance of the force transmitting portion.
Another object of the invention is to provide a pretensioner mounted in a housing together with a cylinder and a force transmitting portion to be integrated with a force transmitting apparatus.
Another object of the invention is to provide a pretensioner integrated with a force transmitting apparatus comprising a clutch apparatus of a new structure to secure the cooperation between a reel shaft and the clutch disk for receiving the force of a force transmitting portion.
Still another object of the invention is to provide a pretensioner integrated with a force transmitting apparatus further comprising a guider for enabling the smooth webbing of a safety belt to be withdrawn based on the operating of the pretensioner, thereby securing a predetermined traveling distance of the force transmitting portion.
As described above, according to the invention a safety belt retractor including a reel rotatably mounted on an U-shaped bracket to perform the webbing operating of a safety belt, a locking portion for restraining the rotating of the reel cooperating with a ratch gear formed on one side of the reel in an abnormal state of a vehicle, a spring portion including a spring of a clock spring type mounted on the other side of the reel to enable the reel to wind the belt thereon and a pretensioner mounted between the inner surface of the spring portion and the U-shaped bracket to reverse-rotate the reel and then withdraw a predetermined length of the safety belt by the force generated in a gas generating apparatus; comprises a pyrotechnic force generating means including a horizontal tube with a propellent charge cartridge mounted therein, a cylinder vertically extended from the other side of the horizontal tube and a piston movably mounted in the cylinder; a housing receiving one end of the cylinder with the horizontal tube being supported on the U-shaped bracket to cooperate with the force generating means in order to reverse-rotate the reel upon the force generating; a force transmitting portion including an arm positioned in the first chamber of the housing, one end of which is directed to the piston in the cylinder and the other end of which is extended out of the cylinder, a pulley rotatably mounted on the axes of the other branched end of the arm and a cable fixed at one end to a predetermined position of the housing, passed through the pulley, wound around the clutch disk by a predetermined turn and fixed at the other end to a predetermined position of the clutch disk; and a pretensioner positioned in a second chamber adjacent to the first chamber, which comprises the clutch disk and a clutch portion, in which the clutch disk includes a circular groove formed around the periphery thereof to allow a predetermined length of the cable to be wound thereon, a plurality of the second coupling projections each having a right-angled surface toward one direction and a slanted surface toward the other direction adjacent to the periphery of one side surface thereof, at least three of coupling grooves cut out at one side in a right-angle and at the other side in a slant angle and a first fixing groove formed to fix the other end of the cable, and the clutch portion includes at least three of first coupling projections forming a slanted surface at one side and a right-angled surface at other side for cooperating with the coupling grooves to allow the clutch disk to be reversely rotated and a plurality of third coupling projections or concaved grooves formed at the positions facing to the second coupling projections on one side surface of the reel.
Also, according to the invention, it is preferable that the three of the first coupling projections in the second chamber are positioned at different arc angles xcex1, xcex2, xcex3 to be staggered from one another properly dividing the circumferential angle of 360xc2x0 so that they are inserted into preferable insertion position of the coupling grooves except.
Also, according to the invention, it is preferable to freely rotate the pulley on the arm of the piston by means of a small bearing and a pin. The reason is because the friction of the cable on the pulley is minimized.
Also, according to the invention, it is preferable to mount the pulley in a manner that masses of both sides of the pulley become eccentric and the weight center of the pulley is slightly inclined toward one direction.
Also, according to the invention, it is preferable to form supporting grooves on both sides of the pulley and mount supporting bars at positions corresponding to at least one predetermined length of the cable, thereby securing the exact traveling length of the cable.
Also, according to the invention, it is preferable that the safety belt retractor further comprises a guider for guiding the safety belt during being wound on or released from the reel, especially for smoothing the webbing due to the reverse-rotating of the reel upon the operating of the pretensioner.